Abstract: This paper presents an experimental study in high speed milling of metal matrix composites (MMCs). Machining tests were carried out on a high speed milling machine by using TiAlN coated tools and chemical vapour deposition (CVD) diamond coated tools. The cutting tool wear was investigated using an optical microscope and a scanning electron microscope (SEM). The experimental results showed that flank wear is the dominant tool wear mode and abrasive wear and adhesive wear appears to be the main wear mechanism. The build-up edge (BUE) exists during the machining process at a certain speeds. Cutting speed is a dominant factor affecting the flank wear. Generally, high cutting speed lead to severe tool wear, but there seemed to be a certain cutting speed which will cause the least tool wear. Furthermore, there exists a cutting speed limit for both TiAlN coated tools and CVD coated diamond tools in high speed milling of MMCs, beyond which the edge chipping will cause the tool failure very soon.

Abstract: Arc ion plating technique PVD ZrN coatings were deposited on YT15 cemented carbide. Microstructural and fundamental properties of the ZrN coatings were examined. The ZrN coated tools (DZ and GZZ) showed much better cutting performance compared to the YT15 uncoated cemented carbide, which is connected with their large hardness increase, and good abrasive wear resistance. The wear surface features of the coatings were examined by scanning electron microscopy. Results showed that the PVD ZrN coatings onto the cemented carbide substrate show high hardness and good adhesion with the substrate. Abrasive wear was found to be the predominant flank wear mechanism for the ZrN coated tools. While the mechanisms responsible for the rake wear were determined to be adhesion.

Abstract: Various methods of surface modification technology are available for yielding high function characteristics such as wear-resistance, lower or higher friction coefficient, corrosion-resistance and thermal-resistance on the surface of the material. Generally, the coating of a hard material like ceramic on the surface of a material is a popular surface modification technology. The physical vapor deposition (PVD) method, which is one of the coating technologies, is widely used because it can be coated at a lower treatment temperature of 470K – 870K. In cutting, e.g. turning, milling, drilling and tapping, coated cemented carbide tools, which have good fracture toughness and wear resistance, seem to be effective tool materials. In this case, the titanium based films (e.g. TiN, Ti(C,N), (Ti,Al)N) are generally used as the coating film. However, the tantalum based films (e.g. TaN, TaC) are not applied as the coating film for cutting tools because the melting point of TaC is higher than that of TiC. Moreover, it is unclear whether TaN coating film can be used as a coating film of WC-Co cemented carbide cutting tools. In this study, to clarify the effectiveness of tantalum (TaN) coating film, we measured the thickness, hardness and scratch strength (critical load measured by scratch tester) of TaN coating film formed on the surface of the substrate which was a cemented carbide ISO K10 by the magnetron sputter ion plating process. The hardened steel ASTM D2 (JIS SKD11) was turned with the TaN and the (Ti,Al)N coated cemented carbide tools. The tool wear of the TaN coated cemented carbide tool was experimentally investigated and compared with that of the (Ti,Al)N coated tool. The following results were obtained: (1) Droplets on the surface of the TaN coating film, which has the K10 substrate, were negligible. (2) The micro-hardness of TaN coating film 2510HV was higher than that of TiN coating film 2090HV, and there was little difference in hardness between the TaN 2510HV and (Ti,Al)N 2710HV. (3) The critical scratch load of TaN coating film over 130N was higher than that of TiN coating film 68N or (Ti,Al)N coating film 73N. (4) In cutting the hardened steel using TaN and (Ti,Al)N coated tools, the wear progress of the TaN coated carbide tool was almost equivalent to that of the (Ti,Al)N coated carbide tool. The above results clarify that the TaN coating film, which is a new type of coating film, has both high hardness and good adhesive strength, and can be used as a coating film of WC-Co cemented carbide cutting tools.

Abstract: Optical, surface and structural properties of ZnO thin films fabricated by reactive radio- frequency (rf) magnetron sputtering and sol-gel coating methods are comparatively investigated. The optical properties of films produced by both techniques have very similar characteristics, however; the surface morphology and degree of crystallinity have different behaviors. The nanostructure columnar zinc oxide thin films can be synthesized by sol-gel coating methods which can have numerous applications requiring larger surface area. Also, the process scalability and large-scale manufacturing of these materials are discussed. It indicated that the nanostructure ZnO thin films can be synthesized with sol-gel methods at wafer levels with nano-grains and improved surface properties compared with reactive rf magnetron sputtering deposition.